PEBBLE BEACH, Calif. -- Jesus Montenegro of Argentina, the 998th-ranked amateur in the world, toppled top-ranked Braden Thornberry of Olive Branch, Mississippi, 2 and 1 in the U.S. Amateur on Wednesday at Pebble Beach as the world's top three amateurs lost in the round of 64.

The 21-year-old Montenegro is coming off his freshman season at Jacksonville State, and he has college coach James Hobbs with him at Pebble Beach as his caddie.

"It was special," Montenegro said. "We didn't play as well as we wanted to, but we had a little edge. My coach was helping when I was missing and things weren't going so good. He helped me a lot going over things. It's my first time playing here. The greens are really good, but it's difficult to put the ball close to the hole."

The 21-year-old Thornberry won the 2017 NCAA individual title for Mississippi.

Justin Suh of San Jose, the No. 2-ranked amateur and an All-American this year as a junior at USC, fell 1 up to Harrison Ott of Brookfield, Wisconsin, a sophomore at Vanderbilt. John Augenstein of Owensboro, Kentucky, a sophomore at Vanderbilt, beat No. 3-ranked Collin Morikawa of La Canada-Flintridge, a senior at Cal, in 19 holes.

Co-medalist Cole Hammer of Houston, Texas, a semifinalist this year in the U.S. Junior Amateur, advanced. The 18-year-old Hammer chipped in for eagle from just off the back green on the 18th to beat Alvaro Ortiz of Mexico 2 up.

"It was a crazy day; it was an absolute grind all day," said Hammer, an incoming freshman at Texas.

Trevor Phillips, 20, of Inman, South Carolina, and a junior at Georgia, and younger brother Trent, 18, who will join his brother on the Bulldogs' golf team as a freshman this year, both advanced. The elder Phillips, playing in his second U.S. Amateur, beat Michael Thorbjornsen of Wellesley, Massachusetts 4 and 3. The younger Phillips advanced with a 3 and 2 victory over Riley Elmes of Lake Oswego, Oregon.

Stewart Hagestad of Newport Beach, the former USC player and the low amateur in the 2017 Masters, made the round of 32 with a 1-up victory over Harry Hall of England.

Noah Goodwin of Corinth, Texas, the 2017 U.S. Junior Amateur titlist, competing in his fourth U.S. Amateur, advanced with a 5 and 4 win over NHL referee Garrett Rank of Canada.